MECHANICS OF ANKLE SPRAINS IN SPORTS

Kendra Sickinger

Objectives Anatomy orientation Surfaces Coefficient of friction Impulse Prevention

What is an ankle sprain? Stretching or tearing of ligaments

surrounding bone Ankle is in unnatural position, uneven

surface, “roll in” Grade I, II, III

Anatomy Orientation

Which is more common?

Friction and Forces

Friction is the force that opposes efforts to slide or roll one body over another

Force needed to plant the foot Surfaces with high coefficients of friction

requires large amount of force Higher coefficients leads to more force

to more injuries

Coefficient of Friction Rolling friction helps soccer

players to determine how the ball will react on turf vs. grass

Smaller coefficient, easier for the surfaces to begin rolling or slide

Coefficient of 0.0 would indicate a frictionless surface

Friction is dependent on the force holding the surfaces together and force needed to slide one surface over

Coefficient decreases as f(max) decreases

Why do ankle sprains happen? An unnatural twisting motion Planted awkwardly Ground is uneven Unusual amount of force is applied to the joint Unaware Supporting weight and ankle size

Turf Surface High friction between

cleat and playing surface Greater number of

injuries due to friction Hardness/sticky feeling In 2000 created synthetic

infill artificial surface (eg. FieldTurf, AstroPlay) to create less friction

How this ties to impulseF= m(Vf-Vi)

T

Different surfacesGrass Sand

Speed of play is slower (time)

Landing on softer surface vs. indoor court

Harder to maintain Court rules

Unaware of uneven surfaces

time

F= m(Vf-Vi)T

Gymnastics Surface Padded surface Fast velocities High impact forces Small margin of error Dorsiflex Overuse

Tied To Class

Learned that friction is a force that acts upon opposite direction

Too much friction can cause injury Coefficient gets higher, more friction Increasing friction = better performance

as well as decreasing frictionF= m(Vf-Vi)

TOnly impact on force is time

Prevention Stability/balance exercises Ankle braces Proper shoe Strengthen muscles around ankle Range of motion

Conclusion Turf vs. grass is still controversial Force and friction Friction surface plays a dominate role in

ankle sprains in sports Impulse equation Never 100% prevent

F= m(Vf-Vi)T

References Drakos, M. (2008). Artificial Turf: Does it Increase the Risk of

Sports Injuries? Hospital for special surgery. http://www.hss.edu/conditions_artificial-turf-sports-injury-prevention.asp

Goal-Tek Innovations ltd. Soccer Safety E- Book. Turf Field Hazards (5). http://www.goal-tek.com/SoccerSafety_ch05.asp

Kinesiology: Scientific Basis of Human Motion. 11th ed. New York: McGraw-Hill, 2008. Print.

Nicholas Institute of Sports Medicine and Athletic Trauma (2007) Ankle Sprains. http://www.nismat.org/ptcor/ankle_sprain

Vormittag, K., Calonje, R., & Briner, W. W. (2009) Foot and ankle injuries in the bare sports. American College of Sports Medicine, 8(5).